This book is pretty hard to find. But you can get a PDF of Chapter Six, "A Testimony of Lies" From Human Events. The chapter discusses his testimony to the Senate in '71 and the Vietnam Veterans Against the War (VVAW) group.
I'd say it's devastating to compare these actions with his pride of service at the convention in Boston. There are a lot of vets, furthermore, who are not willing to forget. POWs were tortured with his words and pictures by their captors. "See, everybody knows you are war criminals!"
The chapter ends with some striking quotes, like:
All I can say is that when I leave here today, I’m going down to the Wall to tell my two crew members it’s not true, and that they and the other forty-nine Swiftees who are on the Wall were then and are still now the best.
—Robert Brant